It relates more particularly to pumps intended to connect the inside and the outside of a pharmaceutical product vessel, the product being for example a liquid or gel of low viscosity used in the treatment of adult men having a testosterone deficiency.
It is important, in the treatment of certain complaints, to ensure that the quantity of pharmaceutical product dispensed by a device with a pump for dispensing this product, or dose to be dispensed, is always substantially identical.
In the following, an element is qualified as upstream or downstream as a function of the direction of the flow of the product during dispensing thereof in this element.
Document EP 1 578 537 discloses a pharmaceutical product dispensing device provided with a pump intended to connect the inside and the outside of a pharmaceutical product vessel. It comprises an upstream product passage end intended to extend into the vessel and a ball-type nonreturn valve extending downstream of the upstream end, the valve switching between closure and passage configurations. This device is intended to be used “head up”.
This device makes it possible to efficiently dispense the same dose of product as long as the vessel is sufficiently full, but when the quantity of product remaining in the vessel corresponds to no more than a few doses (this is referred to as the end of life of the device), it is perceived that these are not as regular as the doses dispensed beforehand.
Specifically, during the initial mounting of the device, air is retained in the pump.
Subsequently, the devices are packaged in cardboard boxes which may be stored in random orientations.
Consequently, the device may be stored, before its first use by the patient, in a position in which the vessel is above the upstream end (when the device is “head down” with respect to its position allowing the product to be dispensed), which means that the ball of the nonreturn valve is moved downward under the effect of gravity and no longer completely closes the passage of the upstream end. The effect of this is that the air contained in the pump manages progressively to pass, from the upstream end, into the vessel. Although a majority of this air is expelled during the first use of the device, another portion can be trapped at the bottom of the vessel, and thus have an influence on the content of the last doses to be dispensed.